Camera system

ABSTRACT

A camera system for communicating data between a micro computer on a camera body and a zoom lens mounted to the camera body, wherein at least exposure data on the diaphragm is transmitted from the zoom lens to the micro computer of the camera body, and wherein the zoom lens includes a position detecting device for detecting one of the divided focal length steps corresponding to a focal length of the zoom lens, a memory for storing data peculiar to the zoom lens, and an arithmetic operating device for calculating the exposure data on the diaphragm in accordance with the data of the position detecting device and the memory.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a camera system that functions tocommunicate data between a camera body and a photographing lens.

2. Description of Related Art

In a recent single lens reflex camera having an automatic focusingdevice, information peculiar to a photographing lens, such as openF-number data used in an automatic exposure function or an automaticfocusing function, is sent as electrical signals from the photographinglens to a CPU (central processing unit) of a camera body.

Information peculiar to the photographing lens is stored in a lens ROMprovided in the photographing lens. The photographing lens and thecamera body are provided with electrical contacts on a lens mount and abody mount to transmit and receive signal information between thephotographing lens and the camera body, respectively. The body CPUtransmits and receives the signal information to and from the lens ROMthrough the electrical contacts and reads the data stored in the lensROM. A clock pulse is outputted from the camera body to send addresssignals from the body CPU synchronously therewith, so that predetermineddata can be output from the lens ROM in accordance with the addresssignals.

However, in an arrangement in which a motor is provided also in thephotographing lens to control the power zooming etc., if all the controloperations in the photographing lens are effected by the body CPU, thereis an over load thereon. In particular, in a single lens reflex camerain which various kinds of photographing lenses are exchangeably mountedto the same camera body, the body CPU must read different parameters,depending on the photographing lenses from the associated lens ROM's andperform predetermined arithmetic operations in accordance with the readparameters thereby to control the photographing lenses. This makes quickoperations impossible or next to impossible.

In a zoom lens, a minimum Av value (open diaphragm F number) increasesas the focal length increases. Namely, the relationship between theminimum Av value and a focal length is represented by a linear function.Accordingly, the minimum Av values corresponding to the focal lengthsare all stored in the ROM of the photographing lens. Consequently,various data, including the minimum Av values are stored in a ROM sothat the memory (capacity) of the ROM, in which the data can be writtenis reduced. Therefore, the stored data must be partially erased, or alarge ROM must be used instead of a conventional ROM to write new data.

SUMMARY OF THE INVENTION

The primary object of the present invention is to provide a camerasystem in which the load of operations on a camera body side is reducedand all diaphragm value exposure data is not stored in a ROM, but iscalculated and used in accordance with need.

The basic concept of the present invention resides in that all of theexposure data on the diaphragm value are not stored in the ROM, but arecalculated when needed.

To achieve the object mentioned above, according to the presentinvention, there is provided a camera system for data communicationbetween a micro computer provided in a camera body and a zoom lens thatis mounted to the camera body, wherein the zoom lens, at the least,exposure data to the micro computer of the camera body, and wherein thezoom lens comprises a position detecting means for detecting one of aplurality of divided focal length steps to which an optional focallength of the zoom lens belongs, means for storing the data peculiar tothe zoom lens, and an arithmetic operation means for calculating theexposure data in accordance with data of the position detecting meansand the memory means.

In this arrangement, the load of operations on the micro computer of thecamera body can be reduced, and the arithmetic operation meanscalculates the exposure data of the diaphragm value only when it isneeded. Accordingly, it is not necessary to always store the exposuredata in the ROM. Thus, the effective memory (storage capacity) of theROM can be increased. The exposure data can be easily and accuratelycalculated when necessary.

The present disclosure relates to subject matter contained in Japanesepatent application No. HEI 2-127938 (filed on May 17, 1990) which isexpressly incorporated herein by reference in its entirety.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described below in detail with reference to theaccompanying drawings, wherein:

FIG. 1 is a block diagram of a single lens reflex camera having a camerasystem according to the present invention;

FIG. 2 is a block diagram of a main circuit arrangement of aphotographing lens shown in FIG. 1;

FIG. 3 is a block diagram of a main circuit arrangement of a camera bodyshown in FIG. 1;

FIG. 4 is a diagram showing a relationship between focal lengths andexposure data;

FIG. 5 is a flow chart of arithmetic operations of the focal lengthperformed by the camera of FIG. 1;

FIG. 6 is a flow chart of arithmetic operations of a drive pulsecoefficient K value;

FIG. 7 is a flow chart of arithmetic operations of the drive pulsecoefficient K value according to another embodiment of the presentinvention;

FIG. 8 is a diagram showing the relationship between the variation ofthe K value and the movable range of a distance ring; and,

FIG. 9 is a flow chart of arithmetic operations of the drive pulsecoefficient K value of a single focus macro lens.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a single lens reflex camera of a camera system according toone aspect of the present invention.

Camera body 1 has a main CPU 10 and an indication CPU 11. The main CPU10 generally controls the whole camera system and performs arithmeticoperations of various data necessary for taking a picture. Theindication CPU 11 functions not only as an interface (datacommunication) to data that is inputted by switch members and totransmit and receive data (signals) to and from a photographing lens(zoom lens) 2, but also as a controller to control the indication of thephotographing data.

The indication CPU 11 is connected to an LCD panel 12 which indicatesphotographing data and a DX code input circuit 13 which selectivelyreads at least ISO sensitivity data of a film from DX codes provided ona surface of a patrone of a film.

A light receiver 14, which receives light incident thereon through thephotographing lens 2 and outputs analog signals in accordance with theamount of light received, is connected to the main CPU 10 through an A/Dconverter 15.

The main CPU 10 is also connected to an exposure control circuit 16,which drives and controls a shutter mechanism (not shown) and adiaphragm mechanism (not shown), etc., in accordance with the inputtedphotographing data. A CCD processing circuit 18 is connected to the mainCPU 10 and detects a focusing of the photographing lens 2 in response todata (focal point data) of an object to be photographed that isoutputted from an automatic focusing CCD object distance measuringsensor 17. An AF motor control circuit 20, also connected to the mainCPU 10, which drives an AF motor 19 for carrying out the focusing of thephotographing lens 2 in conjunction with an AF pulser 21 which detectsthe angular displacement of the AF motor 19 and generates pulsescorresponding to the angular displacement. The object distance measuringsensor 17 receives light of the object to be taken. The light is madeincident thereon through the photographing lens 2 to output apredetermined focus data signal.

The AF motor 19 transmits the drive power to the photographing lens 2through a coupler 19a that is provided on a body mount BM of the camerabody so as to be extended from the camera body and a coupler 31aprovided on a lens mount LM of the photographing lens 2 when theconnection between the couplers 19a and 31a is established.

A battery 22 powers not only the electronic components and electroniccircuits in the camera body 1, but also the electronic components andelectronic circuits in the photographing lens 2.

The photographing lens 2 has a focusing mechanism 31 which rotates afocus adjusting cam ring (not shown) to relatively move focusing lensgroups in the optical axis direction, so as to effect a focusingoperation. A zooming mechanism 32 rotates a zoom ring (not shown) torelatively move at least two groups of variable power lenses in theoptical axis direction to effect a zooming operation.

The focusing mechanism 31 is connected to the coupler 31a, which iselectrically connected to the coupler 19a when the photographing lens 2is attached to the camera body 1 to transmit the rotational drive of theAF motor 19 to the focusing mechanism 31. The focusing mechanism 31rotates the focus adjusting cam ring to affect the focusing. Thecouplers 19a and 31a are disconnected by a disengaging means (notshown), so that a photographer can manually rotate a focus adjustingoperation ring to adjust the focus in a manual focusing mode.

The zooming mechanism 32 is driven by a PZ (power zoom) motor 34, whichis in turn driven and controlled by a power zoom motor driving portion33. The operation of the PZ motor driving portion 33 is controlled inthe power zoom mode by the lens CPU 30 or a power zoom switch SWPZ2 (SeeFIG. 2), and is driven in the manual zoom mode by a manual operation ofa photographer. The mode selection between the power zoom mode and themanual zoom mode is controlled by a zoom switch SWPZ1. The control iseffected by a switching means.

To the input ports of the lens CPU 30 are connected a PZ pulser 35 whichdetects the displacement of the PZ motor 34, a distance code plate 36which reads the position data of the focus adjusting cam ring (focusinglens groups) driven by the focusing mechanism 31 (which detects thedivided focal length steps at a specific focal length), a zoom codeplate 37 which reads the position data (focal length data) of thezooming cam ring (variable power lens groups) driven by the zoomingmechanism 32, a zoom operation code plate 38 which inputs data withregard to the direction and speed of the power zooming by the operationof a zoom operation switch, a lens judgment code plate 39 which judgesthe kind of photographing lens (such as for example, zoom lens, singlefocus lens, or single focus macro lens, etc) and the data stored in theROM, and a data setting portion 40 which is made of a code plate andwhich outputs data on a K value at a telephoto extremity and data on asingle focus macro mode at an infinite object distance. In theillustrated embodiment, "K value" (automatic focusing drive pulsecoefficient) means a value used for the automatic focusing operation ofthe lens which can be moved by the AF motor, and is the number of pulsesof the AF pulser 21 necessary for moving an image plane formed by thephotographing lens 2 through a unit displacement (e.g., 1 mm).

The zoom code plate 37 and other code plates, per se known, are usuallymade of code plates secured to a cam ring and have brushes mounted to astationary ring with a plurality of electrical contacts which areindependently brought into sliding contact with the codes of the codeplates. The positions of the cam rings are usually detected as bitinformation by a combination of the codes with which the electricalcontacts of the brushes come into contact. The focal length is dividedinto a plurality of equidistant focal length steps.

A lens interface 41 is connected to a data input terminal of the lensCPU 30. Data communication between the lens CPU 30 and the indicationCPU 11 is affected through the lens interface 41, to which a macro codeportion 42 is connected to input macro data thereto in the macro mode.

The lens CPU 30 performs the arithmetic operation to obtain variousdata, such as a present focal length, a present object distance, etc.The data necessary for the arithmetic operation is stored in an internalROM (not shown) of the lens CPU 30.

Circuit of Camera Body

The circuit arrangement of the camera body 1 will now be described belowin detail with reference to FIG. 3.

The voltage of battery 22, which is controlled by a regulator 23 andbacked up by a super capacitor 23, is supplied to a terminal VDD1 of theindication CPU 11. The indication CPU 11 is always activated at aconstant voltage input to the terminal VDD1.

Terminal P1 of the indication CPU 11 is connected to a DC/DC converter25 which turns the power source of the main CPU 10 ON and OFF. Aphotometer switch SWS, which is turned ON when a shutter button (notshown) is pressed halfway, connects terminal P2 to the DC/DC converter25. Furthermore, terminals P3 and P4 of the indication CPU 11 areconnected to a release switch SWR which is turned ON when the shutterbutton is fully depressed and a lock switch SWL which is turned ON whenthe camera is brought into a suitable photographing position,respectively.

The DC/DC converter 25 is actuated when the lock switch SWL is turned ONand when the photometer switch SWS or the release switch SWR is turnedON. in accordance with a command from the indication CPU 11 uponinputting the lens data from the photographing lens 2, the DC/DCconverter 25 applies terminal VDD1 of the main CPU 10 with a referenceconstant voltage, to thereby actuate the main CPU 10.

Terminals P5, P6, P7, P8 and P9 of the indication CPU 11 are connectedto a mode switch SWM, drive switch SWDR, exposure correction switchSWXV, up-switch SWUP and down-switch SWDN, respectively.

The indication CPU 11 operates in accordance with the operative andinoperative states of switches SWM, SWDR, SWXV, SWUP, and SWDN. Forinstance, exposure modes, including, for example, a programed exposuremode, an automatic exposure mode, and a manual exposure mode, areselected in accordance with the operation of the mode switch SWM.Similarly, drive modes, including, for example, a single shot mode, anda continuous shot mode, are selected in accordance with the operation ofthe drive switch SWDR. The selection modes can be varied, for example,in accordance with the operation of the up-switch SWUP and down-switchSWDN at a position in which the exposure modes or the drive modes can beselected.

The indication CPU 11 makes it possible to change the exposurecorrection value when the exposure switch SWXV is turned ON. Namely, theexposure correction value can be increased and decreased in accordancewith the operation of the up-switch SWUP and the down-switch SWDN,respectively.

The indication CPU 11 has a group of indication control terminals PSEGthat is connected to an indicating LCD 12 through a bus line. Theindicating LCD 12 indicates necessary photographing data in accordancewith a command of the indication CPU 11 when the lock switch SWL isturned ON.

Seven terminals P10 through P16 of the indication CPU 11 are connectedto electrical contacts Fmin1, Fmin2, Fmin3, Fmax1, Fmax2, A/M, and Conton the body mount BM of the camera body, respectively. Terminal P18 ofthe indication CPU 11 is connected to a switch circuit 26.

The electrical contacts Fmin1, Fmin2 and Fmin3 also function ascommunication terminals for data communication between the photographinglens 2 and the indication CPU 11. Namely, the electrical contacts Fmin1,Fmin2 and Fmin3 comprise a serial clock signal inputting and outputtingterminal SCK, a data transmitting and receiving terminal DATA, and areset signal outputting terminal RES, respectively.

Terminals P10, P11 and P12 of the indication CPU 11 are always pulled upwithin the indication CPU 11.

The output of the switch circuit 26 is connected to a terminal VBATT,and functions as a switch for establishing and breaking an electricalconnection between the battery 22 and terminal VBATT in accordance withthe level of terminal P18. Terminal Gnd of the indication CPU 11 isconnected to ground terminal Gnd of the battery 22.

The indication CPU 11 and the main CPU 10 communicate with each otherthrough serial terminals SCK, serial-in terminals SI and serial-outterminals SO. In conventional data communication, data is transferredusing command codes, as shown in Table 1 below. In Table 1, the leftcolumn represents data which is outputted from the indication CPU 11 tothe main CPU 10, and the right column represents data which istransferred from the main CPU 10 to the indication CPU 11. This data isset based on the measurements of the object luminance and the objectdistance, etc. controlled by the main CPU 10.

                  TABLE 1                                                         ______________________________________                                        Indication CPU 11 → Main                                                                Main CPU 10 → Indication                              CPU 10           CPU 11                                                       ______________________________________                                        Mode Setting Data                                                                              Indication Tv, Sv data                                       Drive Setting Data                                                                             Film Sensitivity Data                                        Exposure Correction                                                                            AF Accommodation                                             Setting Data     Pulse No. Data                                               Lens CPU Data    AF Return Completion Data                                    Setting TV, SV Data                                                           AF Accommodation Data                                                         AF Return Code                                                                AF Return Pulse No. Data                                                      AF Accommodation and                                                          Return Codes                                                                  ______________________________________                                    

Contact groups PA, PB, PC, PD, PE and PF of the main CPU 10 areconnected to an A/D converter 15, the exposure control circuit 16, theCCD processing circuit 18, the AF motor control circuit 20, the AFpulser 21, and the DX code input circuit 13, respectively.

Terminal P20 of the main CPU 10 is connected to first AF switch SWAF1,which selects an auto focus mode in which focusing is automaticallyaffected by the AF motor 19 and a manual focus mode in which focusing ismanually affected by a photographer. Terminal P21 of the main CPU 10 isconnected to a second AF switch SWAF2, which switches the mode of theshutter release between a focus priority mode and a release prioritymode. The first and second AF switches SWAF1 and SWAF2 are mechanicallyassociated with each other, so that for example, when the manual focusmode is selected by the first AF switch SWAF1, the second AF switchSWAF2 is switched to the release priority mode. Namely, when the firstAF switch SWAF1 is turned ON, the second AF switch SWAF2 is turned OFF.

Circuit of Photographing Lens

The circuit arrangement of the electrical system provided in thephotographing lens 2 will now be explained below, with reference to FIG.2.

The lens mount LM of the photographing lens 2 is provided withelectrical contacts VBATT, CONT, RES (Fmin3), SCK (Fmin1), DATA (Fmin2),GND, Fmax1, Fmax2 and A/M, which correspond to the associated electricalcontacts provided on the body mount BM when the photographing lens 2 isattached to the camera body 1. Although the arrangement of theelectrical contacts of the lens mount LM is not identical to that of thebody mount BM, for the purpose of clarification, the electrical contactsof the lens mount are electrically connected to the correspondingelectrical contacts of the body mount with the same reference numerals.

Contact VBATT on the lens side is connected to the PZ driver 33, so thatthe power of the battery 22 is directly supplied to the PZ motor 34through the contact VBATT by the switching operation of the PZ driver33.

Contacts Fmax1 and Fmax2 of the lens side also function as a steadyinformation transmitting means for transmitting a maximum F-number dataof two bits to the camera body, similar to those provided on aconventional AE lens. Namely, contacts Fmax1 and Fmax2 on the lens sideare grounded through switches SWmax1 and SWmax2, so that maximumF-number (minimum diaphragm value) data is formed in accordance with acombination of the levels of the switches SWmax1 and SWmax2 depending onthe ON/OFF states thereof. The combinations of the levels of contactsFmax1 and Fmax2 on the lens side and the maximum F-number are shown, byexample, in Table 2 below:

                  TABLE 2                                                         ______________________________________                                        F NO.           Fmax2   Fmax1                                                 ______________________________________                                        22              0       0                                                     32              0       1                                                     45              1       0                                                     ______________________________________                                    

Contact A/M on the lens side functions to send auto/manual informationof the diaphragm to the camera body 1. This contact is grounded througha selection switch SWA/M. The selection switch SWA/M operates inassociation with the rotation of a diaphragm ring (not shown) of thephotographing lens 2, so that when the diaphragm ring is in the autoposition and the manual position, the selection switch is turned ON andOFF, respectively.

Contacts Fmin1, Fmin2, and Fmin3 on the lens side function not only as asteady information transmitting means for transmitting the open(minimum) F-number information of three bits to the camera body 1,similarly to those provided on an existing (old) AE lens, but also asdata communication contacts between the camera body and thephotographing lens. The relation between the levels of the contactsFmin1, Fmin2 and Fmin3 on the lens side and the minimum F-number isshown, by example, in Table 3 below:

                  TABLE 3                                                         ______________________________________                                        F NO.    Fmin3         Fmin2   Fmin1                                          ______________________________________                                        1.4      0             0       0                                              1.7      0             0       1                                              2        0             1       0                                              2.5      0             1       1                                              2.8      1             0       0                                              3.5      1             0       1                                              4        1             1       0                                              4.5      1             1       1                                              ______________________________________                                    

To provide both the steady information transmitting function and thedata communication function on the contacts Fmin1, Fmin2 and Fmin3 onthe lens side, these contacts are connected to PNP transistors Tr1, Tr2and Tr3, respectively. The PNP transistors Tr (Tr1, Tr2 and Tr3) areconnected at the emitters thereof to the lens contacts Fmin1, Fmin2 andFmin3, and at the bases thereof to contact CONT through fuse portionsH1, H2 and H3, so as to establish and break the connection,respectively. The collectors of the transistors are grounded. It ispossible to provide the fuse portions H1, H2 and H3 between the emittersand the lens contacts Fmin (Fmin1, Fmin2 and Fmin3).

The indication CPU 11 causes a voltage at contact CONT to drop to groundin order to obtain the open F-number data from the lens contacts Fmin1,Fmin2 and Fmin3. As a result, a transistor (or transistors) Tr to whichthe fuse portion(s) is (are) connected is (are) turned ON, so that theemitter(s) of the transistor(s) which has (have) been turned ONbecome(s) a high level "H", and the emitter(s) of the transistor(s)which has (have) not been turned ON become(s) a ground level or lowlevel "L". Namely, the transistors Tr are selectively turned or OFF inaccordance with the connection of the fuse portions H1, H2 and H3 so asto change the level of the emitters thereof. Consequently, the three-bitopen F-number data is output to the lens contacts Fmin1, Fmin2, andFmin3.

Terminals CONT, RES, SCK, DATA and GND of the lens interface 41 isconnected to terminals CONT, Fmin3, Fmin1, Fmin2 and GND on the lensside, respectively.

Lens contact CONT is connected to the bases of the transistors Tr and toterminal CONT of the lens interface 41, as mentioned above. Theswitching of the power supply from terminal CONT of the lens interfaceis affected through the lens terminal Fmin3. After the data on the openF-number is transferred, when terminals CONT and RES (lens terminalFmin3) become levels "H" and "L", respectively, power is supplied to thelens CPU 30.

Terminal VDDB of the lens interface 41 is connected to terminal VDD ofthe lens CPU 30 through capacitor C2, so that a constant voltagesupplied from the terminal CONT of the camera body 1 is also supplied tothe lens CPU 30.

Terminals DIS1, DIS2 and DIS3 of the lens interface 41 are connected toa distance code plate 36, so that distance data signals of an objectdistance corresponding to the position of the focusing cam ring drivenby the focusing mechanism 31 are inputted to terminals DIS1, DIS2 andDIS3.

Terminal MACRO of the lens interface 41 is connected to macro codeportion 42, which functions as a macro switch and which is turned ONwhen the zoom operation ring is actuated to switch the photographinglens 2 to the macro mode.

The input and output terminals of the lens interface 41 are connected tocorresponding input and output terminals of the lens CPU 30. Resetterminal RESB, clock terminal CLK, serial-in terminal SIS, serial-outterminal SOS, terminal CE, terminal SOE, terminalφ IN, and terminalKAFEND, of the lens interface 41 are connected to reset terminal RESET,serial clock terminal SCK, serial-out terminal SO, serial-in terminalSI, terminal P43, terminal P40, terminal PCL, and terminal POO, of thelens CPU 30, respectively. Terminal CRES of the lens interface 41 isgrounded through a delay capacitor C1.

Lens CPU 30 controls a PZ driver 33 that is connected to a controlterminal thereof. The lens CPU 30 is also connected to a PZ pulser 35and a lens discriminating code 39 which outputs data with regard to thelens type (old lens, new lens, etc.).

Terminals P30, P31, P32 and P33 and terminals P62 and P63, of the lensCPU 30 are connected to codes of a zoom code plate 37 (positiondetecting means). The zoom code plate 37 functions as a second distancecode plate B at the single focus macro mode.

Terminals P21 through P29 are connected to various switches, includingthe automatic focusing switch SWAF and the power zoom switches SWPZ1 andSWPZ2, etc. Terminals P50 through P53, P60 and P61 of the lens CPU 30are connected to data setting portion 40.

Lens CPU 30 includes a lens judging means 45, a data storing means 46, adata table 47, a telephoto extremity focal length storing means 50, andan arithmetic operating means 44.

The lens judging means 45 determines whether the attached lens is an oldlens or a new lens, a zoom lens, a single focus lens, or a single focusmacro lens etc., in accordance with the data of the lens discriminatingcode 39. An old lens does not have a lens CPU. On the other hand, a newlens contains a lens CPU therein. A new lens is illustrated in FIGS. 1and 2.

The data storing means stores a common ratio and a common difference forgeometrically and arithmetically dividing a focal length range of thephotographing lens 2. The data storing means stores gradients "m₁, m₂ "which respectively show the minimum A_(v) value and the maximum A_(v)value, and the minimum A_(v) value "A_(v) minW" at the wide angleextremity (or "A_(v) minT" at the telephoto extremity). Furthermore,when the photographing lens 2 is a macro lens, the data storing means 46stores a common ratio for geometrically and arithmetically dividing thefocal length range of the macro lens.

Coefficient data (r^(x))² necessary for calculating the K VALUEcorresponding to the photographing lens is pre-stored in the data table47 as Tables 1 and 2.

The telephoto extremity focal length storing means 50 stores the focallength of the photographing lens at the telephoto extremity.

The arithmetic operating means 44 calculates the focal length and thedrive pulse coefficient K VALUE's at respective focal length steps uponzooming, and the K value at macrophotographing in accordance with thedetermination of the lens by the lens judging means 45, the levels ofterminals P30 through P33, P62 and P63, the K VALUE of the data settingportion 40 at the telephoto extremity, and the K VALUE at the singlefocus macro mode, and stores the calculated data in a RAM. Furthermore,the arithmetic operating means 44 designates the addresses for the dataon gradients "m₁, m₂ ", the maximum and minimum A_(v) values at the wideangle extremity. Then, when necessary, by using the data, the arithmeticoperating means 44 calculates the maximum A_(v) value and the minimumA_(v) value.

The photographing lens 2 has a clock pulse generating circuit 43 that isconnected to clock terminals X1 and X2 of the lens CPU 30. The lens CPU30 operates synchronously with the clock pulses generated by the clockpulse generating circuit 43.

As mentioned above, on the camera body side, after terminal CONT dropsto level "L" and the open F-number is read, both the terminals CONT andRES (Fmin3) become level "H" so as to reset the lens CPU 30.

When the reset is released, the lens CPU 30 begins the old communicationin accordance with the clock pulses of the camera body 1. Thiscommunication is carried out by the lens interface 41. In theillustrated embodiment, 19 bytes of data is sent to the camera body 1.

Upon completion of the communication, terminal KAFEND of the lensinterface 41 becomes level "L", which comprises a communicationcompletion signal. Consequently, the lens CPU 30 waits for renewal dataof the communication from the camera body 1.

When the lens CPU 30 receives the renewal communication data from thecamera body 1, terminal DATA (Fmin2), which has been at level "H"becomes level "L" and then becomes level "H" again, so that the camerabody can commence the new communication. Note that terminal CONT is heldHIGH and terminal RES is held LOW when the lens CPU 30 is firstactivated.

The new communication which commences upon completion of the oldcommunication is carried out directly between the lens CPU 30, theindication CPU 11 and the main micro computer 10 without the lensinterface 41. The data is transmitted from the lens CPU 30 to the mainmicro computer 10 and the indication CPU 11 or from the main microcomputer 10 and the indication CPU 11 to the lens CPU 30, in accordancewith the command code of the indication CPU 11. An example of the datacommunication between camera body 1 and photographing lens 2 is shown inTable 4.

The new data communication is affected synchronously with the clockpulse output from the photographing lens 2.

                  TABLE 4                                                         ______________________________________                                        Lens → Camera Body                                                     AF Data              0011.0001 (31H)                                          AE Data              0011.0010 (32H)                                          All Data             0011.0011 (33H)                                          Every One Byte       1010.XXXX (5XH)                                          Lens Data 1          0110.0000 (60H)                                          Lens Data 2          0110.0001 (61H)                                          Camera Body → Lens                                                     Focal Length Data fWide                                                                            0110.0010 (62H)                                          Focal Length Data fTele                                                                            0110.0011 (63H)                                          Focal Length Data fX(present)                                                                      0110.0100 (64H)                                          Lens Drive Data      0110.0110 (66H)                                          Lens Accommodation   1001.0010 (90H)                                          Lens Return          1001.0001 (91H)                                          PH ON                1001.0010 (92H)                                          PH OFF               1001.0011 (93H)                                          ______________________________________                                        Lens Data 1  Lens Data 2    Lens Drive Data                                   60H          61H            66H                                               ______________________________________                                        Bit 7 PH Demand  Lens CPU       fW extremity                                  Bit 6 AF A/M                    fT extremity                                  Bit 5 PZ A/M     Lens Internal PZ                                             Bit 4 PZ P/A                                                                  Bit 3 PZ MODE                   PZ Far                                        Bit 2 SET SW                    PZ Near                                       Bit 1 Lens A/M   Lens                                                         Bit 0 Lens O/C   Version                                                      ______________________________________                                    

Calculation of Exposure Data on Diaphragm

The following discussion will be directed to the calculation of exposuredata, such as a minimum Av values or a maximum Av values, by thearithmetic operating means 44.

FIG. 4 is a diagram showing the relationship between the focal length ofthe zoom lens, in which the focal length varies within a range of 35 mmthrough 135 mm, and the minimum Av value thereof. In the diagram of FIG.4, the abscissa represents a focal length "fx" and the ordinaterepresents a minimum Av value "Avmin", respectively.

Straight line "H" in FIG. 4, which is a linear function, intersects theordinate "Avmin" at a value of 3.6875. The focal lengths and the minimumAv values corresponding thereto are in a substantially linearrelationship. Although the minimum Av values at the corresponding focallengths are not accurately on the line "H" and are scattered near theline "H", the approximate values of the minimum Av values for thecorresponding focal lengths are obtained from the points on the line"H". In the present invention, the approximate values are corrected tobe used as exposure data.

The linear function of the straight line "H" is represented by thefollowing formula:

    Avmin=m.sub.1 ·f.sub.x +3.6875                    (A)

where m₁ designates a gradient of the line "H".

From this, the gradient ml is given by the following equation:

    m.sub.1 =(A.sub.v min-3.6875)/f.sub.x                      (B)

The gradient "m1" depends on the photographing lens mounted to thecamera body and is stored in a ROM (data storing means 46) of each newlens to be used in the new communication.

The Av values become small and large at the wide angle extremity sideand a telephoto extremity side, respectively. Accordingly, a minimum Avvalue "Avmin" is obtained from the following equation:

    Avmin=AvminW+ΔAvmin·f.sub.x                 (C)

where "AvminW" designates a diaphragm F number at the wide angleextremity (the intersecting value 3.6875 in formula (A), "ΔAvmin"designates the variation of the minimum Av value, and "fx" designatesthe focal length, respectively.

Similarly, the maximum Av value "Avmax" is obtained by the followingequation (D):

    Avmax=AvmaxW+ΔAvmax·f.sub.x                 (D)

where "AvmaxW" designates a maximum, Av value at the wide angleextremity, "ΔAvmax" designates the variation of the maximum Av value,and "f_(x) " designates the focal length, respectively.

Since "ΔAvmin" and "ΔAvmax" are identical to the gradients "m₁ " and "m₂", equations (C) and (D) can be substituted by the following equations,respectively:

    Avmin=AvminW+m.sub.1 ·f.sub.x                     (E)

    Avmax=AvmaxW+m.sub.2 ·f.sub.x                     (F)

The gradients m1 and m2, and the minimum Av and the maximum Av at thewide angle extremity are stored as data that is peculiar to thephotographing lens and are fetched by designating the correspondingaddresses in the data storing means 46 in accordance with a need whenthe arithmetic operating means 44 calculates the minimum Av value"Avmin" or the maximum Av value "Avmax" on the basis of equations (E)and (F) mentioned above.

The data calculated by the arithmetic operating means 44 is stored in aRAM of the lens CPU and is transmitted to the main micro computer 10 andthe indication CPU 11 without going through the lens interface 41 in thenew communication.

Accordingly, it is not necessary to directly store the data, such as themaximum Av values and the minimum Av values in the data storing means46. In accordance with a need, the minimum Av values and the maximum Avvalues can be easily calculated by the arithmetic operating means 44, onthe basis of the data, including the gradients m₁ and m₂, and theminimum Av value AvminW and the maximum Av value AvmaxW at the wideangle extremity, stored in the storing means 46.

Although the minimum Av value AvminW and the maximum Av value AvmaxW atthe wide angle extremity are used in the above mentioned embodiment, itis possible to use a minimum Av value AvminT and a maximum Av valueAvmaxT at the telephoto extremity. In this alternative, the values of"Avmin" and "Avmax" can be obtained by the following equations:

    Avmin=AvminT+m.sub.1 ·f.sub.x

    Avmax=AvmaxT+m.sub.2 ·f.sub.x

Although the exposure data to be calculated are the maximum Av valuesand the minimum Av values in the illustrated embodiments, the exposuredata to be calculated is not limited thereto and can be, for example,effective aperture data of the lens, etc.

In the present invention, since the values of "Avmin" and "Avmax" arecalculated based on the stored data peculiar to the photographing lens,using equations (E) and (F), ineffective data, such as data at point "Z"in FIG. 4 can be calculated. Accordingly, it is also possible to use asimpler linear function represented by the following equation:

    Avmin=m.sub.1 ·f.sub.x

In this equation, point "Z" is a reference point (origin) of thestraight line "H". That is, there is no value "3.6875", unlike equation(A). This contributes to a reduction of the calculation speed of thearithmetic operating means 44.

Calculation of Focal Length

The following discussion will be directed to the arithmetic operatingmeans calculation of focal length in both the zooming and macro modes.

First, zooming ratio R of the photographing lens 2, used togeometrically divide the code of the distance code plate 37 (alsoreferred to as a distance code plate B) into n-codes, is obtained by thefollowing equation:

    R=f.sub.T /f.sub.w                                         (1)

where f_(T) designates a focal length of the lens at a telephotoextremity and f_(w) designates a focal length of the lens at a wideangle extremity, respectively.

Then, common ratio r satisfies the following equation when the code ofthe zoom code plate 37 of the photographing lens 2 is geometricallydivided into n-codes with reference to the telephoto extremity:

    R=r.sup.n-1                                                (2)

From equation (2) above, we have; ##EQU1##

Accordingly, focal length fx at a position x of the zoom ring (0≦x≦n-1,where "0" designates the telephoto extremity and "n-1" designate thewide angle extremity) is determined by the following equation:

    f.sub.x =f.sub.T /r.sup.x                                  (4)

Since the zoom code plate 37(distance code plate B) corresponding to thezoom ring position x has a certain width (band) of codes in which thereis no change of code, in case of a slight angular displacement of thezoom ring, it is necessary to geometrically position the focal lengthf_(x) corresponding to position x at an intermediate position of thezoom code plate 37. To this end, changing points of the zoom code plate37 are obtained as follows:

    f.sub.x-x+1 =f.sub.T /r.sup.x+0.5                          (5)

where f_(x-x+1) is the focal length at a changing point between a zoomcode position x and a zoom code position (x+1) adjacent thereto.

Since the calculation is carried out by the arithmetic operating means44, the memory of the ROM can be reduced, in comparison with the memoryof the ROM in which the focal lengths for every divided code by the zoomcode plate 37(distance code plate B) must be stored.

Upon arithmetically dividing the zoom code plate 37 into n-codes, acommon difference d can be obtained as follow:

    F.sub.dif =f.sub.T -f.sub.w                                (6)

    d=f.sub.dif (n-1)                                          (7)

    f.sub.x =f.sub.T -d.sub.x                                  (8)

where f_(dif) designates the actual amount of zooming, and f_(T)designates the focal length at the telephoto extremity.

Therefore, the changing point can be obtained by the following equation:

    f.sub.x-x+1 =f.sub.T -d(x+0.5)                             (9)

This will be explained below with reference to a flow chart of theoperations shown in FIG. 5.

In step S1, the lens CPU 30 receives the discrimination code inputtedthereto for discriminating the kind of mounted lens from the lensjudging code plate 39.

Thereafter, the zoom code data corresponding to the optional zoom ringposition x is inputted from the zoom code 37 (distance code plate B) tothe lens CPU 30, in step S2.

In step S3, the lens judging means 45 judges whether the photographinglens mounted to the camera body 1 is an old lens or a new lens, a zoomlens, a single focus lens or a single focus macro lens, in accordancewith the data of the lens judging code plate 39.

Thereafter, in step S4, the data of the focal length "f_(r) " in thetelephoto extremity and the common ratio "r" thereof are sent to the RAMfrom the telephoto extremity focal length storing means 50 in accordancewith the determination of the lens judging means 45. Although the focallength "f_(r) " at the telephoto extremity is used as data forcalculation, purposes it is possible to use the focal length in the wideangle extremity or any reference focal length other than those in thetelephoto extremity and the wide angle extremity.

In step S5, the arithmetic operating means 44 calculates the focallength which is geometrically (or arithmetically) dividedcorrespondingly to the lens, in accordance with the data obtained instep S4, based on equation (4) mentioned above, and the calculationresult that is obtained is stored in the RAM. The calculated data of thefocal length is directly transmitted as new communication to the mainmicro computer 10 and the indication CPU 11, without going through thelens interface 41.

Calculation of K VALUE at Zooming

Calculation of the K value (automatic focusing drive pulse coefficient)used in the zooming operation is performed by the arithmetic operatingmeans 44.

In the following description, "K" designates the K value at a focallength F, "G" designates a gear ratio of the focusing mechanism 31 inthe photographing lens 2, "P" designates a number of pulses when thecoupler 19a on the camera body side rotates by one turn, "L" designate alead (mm) of a focusing helicoid, i.e., the displacement when thehelicoid rotates by one turn, "F" designates a FL conversioncoefficient, i.e., the ratio between the displacement of the lens andthe displacement of the image plane, and "f_(T) " designates a focallength at the telephoto extremity.

The K value "K" can be obtained by the following equation: ##EQU2##

Since the photographing lens 2 is a zoom lens, the focal length "F" isdetermined by the following formula; ##EQU3## where f_(x) is the focallength at the position x of the zoom ring, and f_(T) is the focal lengthat the telephoto extremity.

From equations (10) and (11), K value "K_(x) " at the zoom ring positionx (the x-th focal length step from the telephoto extremity) is obtainedby formula (12) below: ##EQU4##

K value "K_(r) " at the telephoto extremity is obtained by the followingequation (13): ##EQU5##

From equations (12) and (13) mentioned above, we have: ##EQU6##

From equations (14) and (4), "K_(x) " in a geometrical division and anarithmetic division can be obtained by the following equations,respectively: ##EQU7##

When the K value is determined in accordance with equations (15) and(16), two methods are used: (a) the common ratio is directly used asdata for calculation, and (b) the coefficient obtained based on thecommon ratio is pre-stored in the ROM (data table 47) as datacorresponding to each code step of the zoom ring position, so that thestored data is fetched from the data table 47 to calculate the K value.

The first method (a) mentioned above will be first explained below, withreference to the flow chart of FIG. 5.

In step S6, the discrimination code is inputted from the lens judgingcode plate 39 to determine the type of lens. Thereafter, the zoom code(or the distance code in the case of a single focus macro lens) in thezoom ring position x (the x-th focal length step from the telephotoextremity) is inputted from the zoom code plate 37(the distance codeplate B).

In step S8, the K value at the telephoto extremity (or infinite objectdistance in case of a single focus macro lens) is inputted from the pin.

Thereafter, the lens judging means 45 determines the type ofphotographing lens required in accordance with the lens discriminationcode from the lens judging code plate 39 in step S9.

In step S10, the common ratio "r" (or "a" in the case of a single focusmacro lens) corresponding to the photographing lens mounted to thecamera body 1 is transferred to the RAM from the data storing means 46.

Thereafter, the arithmetic operating means 44 calculates the K value atthe zoom ring position x, based on the equations (15) and (16) in stepS11. The calculated data is then stored in the RAM. Thereafter, thecontrol returns. This means that the calculation of the K value "K_(x) "is in accordance with the K value "K_(T) " which is steady data inputtedfrom the micro computer port (pin) in the telephoto extremity, thecommon ratio "r" which is ROM data in the lens CPU 30, and the steadydata "x" of the zoom code plate.

The data "K_(x) " thus obtained is directly sent to the main microcomputer 10 and the indication CPU 11 as new communication without goingthrough the lens interface 41. The micro computer 10 controls thephotographing lens 2 in accordance with the data "K_(x) " input thereto.

On the other hand, in the case of method (b) mentioned above, thediscrimination code is inputted from the lens judging code plate 39 todetermine the type of photographing lens 2, in step S12 (FIG. 7).

In step S13, the zoom code (or the distance code in case of a singlefocus macro lens) in the zoom ring position is inputted from the zoomcode plate 37.

In step S14, the K value in the telephoto extremity (or infinite objectdistance in the case of a single focus macro lens) is inputted from thedata setting portion 40.

Thereafter, the lens judging means 45 determines the type of thephotographing lens in accordance with the lens discrimination code fromthe lens judging code plate 39 in step S15.

In steps S16 and S17, the data table (Table 5 or 6) to be used isselected, and the first address (or the first address+zoom code platedata in the case of a single focus macro lens) of the data "D_(x) " ofthe required value "(r^(x))² " is calculated. The value "D_(x) " isfetched from the selected data table and is stored in the RAM in stepS18.

Thereafter, the arithmetic operating means 44 calculates the drive pulsecoefficient K value, based on equation (10) in step S19. The calculateddata is stored in the RAM. Thereafter, control returns. Namely, apredetermined number of parts "(r^(x))² " of equation (15) correspondingto the number of divided focal length steps of the zoom ring is storedin the ROM only as a table data so as to selectively use the data,depending on the kind of photographing lens mounted to the camera body.

Calculation method (b) mentioned above will be explained below in moredetail, with reference to the calculation of the K value, based on a 4bit signal inputted from the zoom code plate 37, by way of examples. Inthe examples below, the data tables are divided into 16 (2⁴ =16)segments. Note that r=1.09375 in Table 5 and r=1.125 in Table 6. Thefour bit signals are inputted from the zoom code plate 37. In theembodiments, the K value is calculated based upon the four bit signals,which means that a maximum of 16 (2⁴ =16) different data can berecorded. Thus, Tables 5 and 6 are divided into 16 parts. However, it isnot necessary to use all 16 parts, because an exchanged-photographinglens requires different numbers (amount) of data, just up to the minimumamount necessary for the zooming ratio of the lens.

In case of "a photographing lens having a zoom ratio of 3", the value(r^(x)) in formula (15) for Table 5 in which r=1.09375 is as follows. Informula (15), K_(X) =K_(T) X (r^(x))². The K value can be obtained usingthe known value K_(T), which corresponds to the X-th from "0" in Table5. The procedure involves finding the value of "x" that is infinitelyclose to "3" (which is the zoom ratio of the lens). In other words,(r^(x))² ≈3. As a result of calculation, one finds that (r¹²)² ≈(2.93)²≈3². As shown in (r¹² ², the data from 0 to 12th (in Table 5), whichmeans 13 different data, are sufficient for a photographing lens havinga zoom ratio of 3.

Consequently, the zoom code is divided into 13 segments.

In case of "a photographing lens having a zoom ratio of 4", the value(r^(x)) in formula (15) for Table 6 in which r=1.125 is as follows. Informula (15), K_(X) =K_(T) X (r^(x))². The K value can be obtained usingthe known value K_(T), which corresponds to the X-th from "0" in Table6. The procedure involves finding the value of "x" that is infinitelyclose to "4" (which is the zoom ratio of the lens). In other words,(r^(x))² ≈4. As a result of calculation, one finds that (r¹²)² ≈(4.11)²≈4². As shown in (r¹²), the data from 0 to 12th (in Table 6), whichmeans 13 different data, are sufficient for a photographing lens havinga zoom ratio of 4.

Consequently, the zoom code is divided into 13 segments. Namely, whenthe value K_(x) is calculated, based on the telephoto extremity K valueand the value D_(x) which are port data K_(T) of the micro computer,based on formula (15), the following equation is satisfied:

    K.sub.x =K.sub.T ×M.sub.x                            (17)

where M_(x) is ROM data at the position x.

                  TABLE 5                                                         ______________________________________                                        ADDRESS1       r = 1.09375                                                    ______________________________________                                        0              1.09375.sup.0                                                  1              1.09375.sup.2                                                  2              1.09375.sup.4                                                  3              .                                                              4              .                                                              5              .                                                              6              .                                                              7              .                                                              8              .                                                              9              .                                                              10             .                                                              11             .                                                              12             .                                                              13             .                                                              14             .                                                              15             .                                                              ______________________________________                                    

                  TABLE 6                                                         ______________________________________                                        ADDRESS2       r = 1.125                                                      ______________________________________                                        0              1.125.sup.0                                                    1              1.125.sup.2                                                    2              1.125.sup.4                                                    3              .                                                              4              .                                                              5              .                                                              6              .                                                              7              .                                                              8              .                                                              9              .                                                              10             .                                                              11             .                                                              12             .                                                              13             .                                                              14             .                                                              15             .                                                              ______________________________________                                    

Calculation of K value in Single Focus Macro Lens

There are two methods of calculation of the K value by the arithmeticoperating means 44, similar to the case of the zooming mentioned above.In the following example, the object distance code is geometricallydivided into n-codes.

The common ratio "a" is given by the following formula: ##EQU8##

where "K_(N) " is the K value at a NEAR extremity of the macro lens, and"K∞" is the K value at a infinite object distance.

The common ratio "a" is stored in the data storing means 46 of the lensCPU 30 and is outputted to the arithmetic operating means 44 at an thatis designated upon calculation of the K value.

When the code of the distance code plate B is geometrically divided inton-codes, a K value "Ky" at an optional object distance "y" (0≦y≦n-1) ofthe macro lens is obtained by the following equation:

    Ky=K.sub.28 × (a.sup.y).sup.2                        (19)

The example below is directed to a 2.8/50 mm macro lens that is mountedto the camera body 1, in which the code of the distance code plate B isdivided into 6 codes.

FIG. 8 shows a diagram in which the abscissa represents a code number ofthe distance code plate B which is equally divided into six (No. 0through 5); the ordinate, the K value, and the position "y" (objectdistance) of the distance ring correspond thereto.

If Kn=256, K∞=100, n=6, we have from the equation (18): ##EQU9##

The common ratio (1.09856) which is stored in the data storing means 46is outputted to the arithmetic operating means 44 at an addressdesignated upon calculation of the K value by the arithmetic operatingmeans 44.

When the common ratio of 1.09856 is inputted into the arithmeticoperating means 44, the K value Ky at the object distance "y" can beobtained from equation (19):

    Ky=100× (1.09856.sup.3).sup.2 ≈176

Since the value "Ky" is an intermediate value of the distance code plateB in a geometrical division, the object distance "y" (from the distancecode plate B and the K value (Ky-y+1) at the changing point (y+1)) isobtained by the following equation:

    (Ky-y+1)=K.sub.∞ × (a.sup.y+0.5).sup.2

Consequently, when the value of (Ky-y+1) for each Ky is calculated,Table 7 is obtained, as follows:

                  TABLE 7                                                         ______________________________________                                        y             Ky     Ky - y + 1                                               ______________________________________                                        0             100                                                                                  110                                                      1             121                                                                                  133                                                      2             146                                                                                  160                                                      3             176                                                                                  193                                                      4             212                                                                                  233                                                      5             256                                                             ______________________________________                                    

The calculation of the K value by the arithmetic operation means 44 inthe macro mode mentioned above will be described below with reference toa flow chart shown in FIG. 9.

For the macro lens, the data of the distance code plate B, instead ofthe zoom code plate 37 is inputted to the lens CPU 30.

In this state, the discrimination code for determining the type of thelens is input from the lens judging code plate 39 to the lens CPU 30 atstep S20.

At step S21, the distance code at the single focus macro mode isinputted to the lens CPU 30 from the distance code plate B.

At step S22, the drive pulse coefficient K value at the infinitedistance extremity is inputted to the lens CPU 30 from the data settingportion 40 through a pin.

At step S23, the lens judging means 45 determines the type of thephotographing lens mounted to the camera body, in accordance with thelens discrimination code inputted from the lens judging code plate 39 atstep S20.

Thereafter, at step S24, the common ratio "a" corresponding to themounted photographing lens is inputted from the ROM (data storing means46) of the lens CPU 30 and is stored in the RAM.

Thereafter, the arithmetic operation means 44 calculates the drive pulsecoefficient K value at the photographing distance (object distance) "y"in accordance with the equation (19) at step S25. After the calculated Kvalue is stored in the RAM, the control is returned.

The calculation data of the K value is directly transmitted as newcommunication to the main micro computer 10 and the indication CPU 11without going through the lens interface 41, so that the main microcomputer 10 drives the AF motor 19 in accordance with the calculationdata in order to perform macro photographing.

Although the invention has been described with reference to particularmeans, materials and embodiments, it is to be understood that theinvention is not limited to the disclosed particulars and extends to allequivalents within the scope of the claims.

We claim:
 1. A camera system for communicating data between a microcomputer in a camera body and a zoom lens mounted to said camera body,wherein at least exposure data on a diaphragm is transmitted from saidzoom lens to said micro computer in said camera body, and wherein saidzoom lens comprises:a position detecting means for detecting one of aplurality of divided focal length steps corresponding to a focal lengthof said zoom lens; a storing means for storing data peculiar to saidzoom lens; and an arithmetic operating means for calculating saidexposure data on said diaphragm in accordance with data of said positiondetecting means and said data in said storing means.
 2. A camera systemaccording to claim 1, wherein said micro computer of said camera bodycomprises an indication CPU and a main CPU.
 3. A camera system accordingto claim 1, wherein said zoom lens comprises a lens CPU.
 4. A camerasystem according to claim 1, wherein said data stored in said storingmeans comprises gradients "m₁ " and "m₂ " of a predetermined functionand minimum Av value "AvminW" at a wide angle extremity, and whereinsaid arithmetic operating means fetches these stored data "m₁ ", "m₂ "and "AvminW" and focal length data "f_(x) " from said storing means andfrom said position detecting means, respectively, to calculate a minimumAv value Avmin, using the following equation:

    Avmin=AvminW+m.sub.1 ·f.sub.x.


5. A camera system according to claim 1, wherein said data stored insaid storing means comprises gradients "m₁ " and "m₂ " of apredetermined function and maximum Av value "AvmaxW" at a wide angleextremity, and wherein said arithmetic operating means fetches thesestored data "m₁ ", "m₂ " and "AvmaxW" and focal length data "f_(x) "from said storing means and from said position detecting means,respectively, to calculate a maximum Av value Avmax, using the followingequation:

    Avmax=AvmaxW+m.sub.2 ·f.sub.x.


6. A camera system according to claim 1, wherein said data stored insaid storing means comprises gradients "m₁ " and "m₂ " of apredetermined function and a minimum Av value "AvminT" at a telephotoextremity, and wherein said arithmetic operating means fetches thesestored data "m₁ ", "m₂ " and "AvminT" and focal length data "f_(x) "from said storing means and from said position detecting means,respectively, to calculate a minimum Av value Avmin, using the followingequation:

    Avmin=AvminT+m.sub.2 ·f.sub.x.


7. A camera system according to claim 1, wherein said data stored insaid storing means comprises gradients "m₁ " and "m₂ " of apredetermined function and a maximum Av value "AvmaxT" at a telephotoextremity, and wherein said arithmetic operating means fetches thesestored data "m₁ ", "m₂ " and "AvmaxT" and focal length data "f_(x) "from said storing means and from said position detecting means,respectively, to calculate a maximum Av value Avmax, using the followingequation:

    Avmax=AvmaxT+m.sub.2 ·f.sub.x.


8. A camera system according to claim 1, wherein said data stored insaid storing means comprises data of an effective aperture of said zoomlens, and wherein said arithmetic operating means calculates a maximumAv value and a minimum Av value, in accordance with said stored data ofan effective aperture and focal length data detected by said positiondetecting means.